Water treatment apparatuses for treating raw water to generate purified water like water purifiers are being variously disclosed. Recently, water treatment apparatuses using electrical deionization, such as electro deionization (EDI), continuous electro deionization (CEDI) or capacitive deionization (CDI), have attracted attention. Among these, the CDI type water treatment apparatus has attracted the most attention.
The CDI method means a method for removing ions (contaminants) by using a principle that ions are adsorbed and desorbed on the surfaces of electrodes by an electrical force. This will be described in more detail with reference to FIGS. 12 and 13. When brine water (or raw water) including ions with a voltage applied to electrodes is made to pass between electrodes, negative ions move to a positive electrode, and positive ions move to a negative electrode as illustrated in FIG. 12. That is, adsorption occurs. Ions contained in the brine water may be removed by such adsorption. However, when the adsorption continues, the electrodes will no longer be able to adsorb ions. In this case, it is necessary to recycle the electrodes by desorbing ions adsorbed to the electrode, as illustrated in FIG. 13. (At this time, recycle water is generated and discharged.
Calcium ions and magnesium ions contained in the brine water are deposited on the electrode to generate scale. Such scale is referred to as inorganic fouling. Also, the fouling may be formed by general bacteria or organics, and this fouling is referred to as organic fouling. However, when the fouling is formed as such, a filter hardly exhibits the performance thereof properly. Thus, the CDI type water treatment apparatuses need to adopt a method for removing the scale formed on electrodes.